I can align the situation to my resources, and focus on any detail level I want without abstraction. To do history I have to look at how deeply I can research and abstract the layers below that.

I can generate detail without guilt. With real history you can fake things up a bit (generic German village names for example) but the possibility of outright contradicting facts that other people in the game (or reading about it) do know does spring up.

I players come to the game with a different vision of the world than mine, that's OK. Because reality is a construct, they don't have to be period experts to play the game "right." In a history game a wildly variant view of the world -- Louis XV invests half the national budget into steam engines or some such -- can drive everyone else's suspension of disbelief off the deep end.

You can elephants charging Europeans -- oh, India, never mind.

The advantage of gaming reality is the challenge:

Getting a well-researched model of the real world across to players in such a way that the can game it realistically is intrinsically hard. Really, why are we trying to do something easy?

Most gamers who would want to play a reality-based game want to get close to the history. We are not talking classic epic fantasy here but a game about the "historically possible." You can't get more possible than reality.

Of course, the instant you set the model going you depart from reality; three things make it historical:

A realistic start point

A model that rewards historical behaviors with historical results

And the hard one: players fitting comfortably within the period and not pressing the bounds of reality too far. Of course, since reality includes the South Sea Bubble, Russian galleys in the Baltic, and the unlikely ending of the Seven Years War (Tzarina Elizabeth dies, replaced by deranged Prussophile successor) I don't know what I am worried about.